import logging
logging.warning('Watch out!') # 将输出到控制台
logging.info('I told you so') # 不会输出
logging.error("an error occurrence！") #将输出到控制台

WARNING:root:Watch out!
ERROR:root:an error occurrence

import logging
logging.basicConfig(filename='example.log',level=logging.DEBUG)
logging.debug('This message should go to the log file')
logging.info('So should this')
logging.warning('And this, too')

DEBUG:root:This message should go to the log file
INFO:root:So should this
WARNING:root:And this, too

# 输入参数 --log=DEBUG or --log=debug
numeric_level = getattr(logging, loglevel.upper(), None)#返回10，否则None
if not isinstance(numeric_level, int):
 raise ValueError('Invalid log level: %s' % loglevel)
logging.basicConfig(level=numeric_level, ...)

import logging
logging.warning('%s before you %s', 'Look', 'leap!')

import logging
logging.basicConfig(format='%(asctime)s: %(levelname)s: %(message)s',level=logging.DEBUG)
logging.debug('This message should appear on the console')
logging.info('So should this')
logging.warning('And this, too')

2017-10-24 14:03:53,671: DEBUG: This message should appear on the console
2017-10-24 14:03:53,690: INFO: So should this
2017-10-24 14:03:53,694: WARNING: And this, too

import logging
logger = logging.getLogger('logger_name')# 创建logger对象
logger.setLevel(logging.DEBUG)
handler = logging.StreamHandler()# 创建 console handler 并设置级别为debug
handler.setLevel(logging.DEBUG)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')# 创建输出格式
handler.setFormatter(formatter)# 为handler添加fromatter
logger.addHandler(handler)# 将handler添加到 logger
logger.debug('debug message')# 'application' code
logger.info('info message')
logger.warn('warn message')
logger.error('error message')
logger.critical('critical message')

import logging
from logging.handlers import TimedRotatingFileHandler
class MylogHandler(logging.Logger):
 def __init__(self,name,level="DEBUG",stream=True,files=True):
  self.name = name
  self.level = level
  logging.Logger.__init__(self,self.name,level=self.level)
  if stream:
   self.__streamHandler__(self.level)
  if files:
   self.__filesHandler__(self.level)
 def __streamHandler__(self,level=None):
  handler = TimedRotatingFileHandler(filename=self.name+".log", when='D', interval=1, backupCount=15)
  handler.suffix = '%Y%m%d.log'
  handler.setLevel(level)
  formatter = logging.Formatter('%(asctime)s %(filename)s[line:%(lineno)d] %(levelname)s %(message)s')
  handler.setFormatter(formatter)
  self.addHandler(handler) #将hander添加到logger上
 def __filesHandler__(self,level=None):
  handler = logging.StreamHandler()
  formatter = logging.Formatter('%(asctime)s %(filename)s[line:%(lineno)d] %(levelname)s %(message)s')
  handler.setFormatter(formatter)
  handler.setLevel(level)
  self.addHandler(handler)
if __name__ == '__main__':
 log = MylogHandler('test')
 log.info('this is a my log handler')